The invention relates to a current-limiting high speed circuit breaker to be used with intermediate voltages and more particularly adapted to direct current electric traction in rolling or stationary equipment.
It is well known that direct current networks, both for traction and in industry, are becoming increasingly complex and powerful. It was necessary to design switching equipment to disconnect currents of ever increasing size and to reduce the cost of maintenance. New generation switchgear must be fast to limit the current and to reduce mechanical and thermal stresses on the entire installation and to reduce wear on its contacts and its spark blow-out chamber. At the present time, switchgear in traction networks comprise very high speed mechanisms to open the contacts and a spark blow-out chamber in which the arc created is confined and cooled. This equipment requires significant expenditures for maintenance and replacing pieces subject to wear.
Various combination of the mechanisms and semiconductors have been proposed but, to our knowledge, none of these has resulted in an industrial application in direct current within the voltage range of interest here, i.e. an the order of 4000 Volts.
The apparatus according to the invention eliminates the aforementioned disadvantages by avoiding the formation of a significant arc by means of the complementary use of semiconductors and of a specific, much more rapid mechanism, referred to hereinafter as a very high speed mechanism.
U.S. Pat. Nos. 3,723,922 and 3,764,944 describe a mechanism intended for a synchronous switchgear apparatus in an alternating network, in which the axial displacement of a disk connected with a mobile contact bridge by means of a center shaft is obtained by repulsion with the aid of helical coils excited by a high current originating in the discharge of a capacitor specifically provided for the purpose. This apparatus, designed for a high voltage alternating current, operates under a high vacuum. It uses exciting coils of a complex manufacture and special devices for the deceleration of the center shaft.